/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.streaming.runtime.translators;

import org.apache.flink.annotation.Internal;
import org.apache.flink.api.common.ExecutionConfig;
import org.apache.flink.api.common.typeinfo.TypeInformation;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.api.dag.Transformation;
import org.apache.flink.api.java.functions.KeySelector;
import org.apache.flink.streaming.api.graph.SimpleTransformationTranslator;
import org.apache.flink.streaming.api.graph.StreamGraph;
import org.apache.flink.streaming.api.operators.StreamOperatorFactory;

import javax.annotation.Nullable;

import java.util.Collection;
import java.util.Collections;

import static org.apache.flink.util.Preconditions.checkNotNull;
import static org.apache.flink.util.Preconditions.checkState;

/**
 * A base class with functionality used during translating
 * {@link Transformation transformations} with two inputs.
 */
@Internal
public abstract class AbstractTwoInputTransformationTranslator<IN1, IN2, OUT, OP extends Transformation<OUT>>
		extends SimpleTransformationTranslator<OUT, OP> {

	protected Collection<Integer> translateInternal(
			final Transformation<OUT> transformation,
			final Transformation<IN1> firstInputTransformation,
			final Transformation<IN2> secondInputTransformation,
			final StreamOperatorFactory<OUT> operatorFactory,
			@Nullable final TypeInformation<?> keyTypeInfo,
			@Nullable final KeySelector<IN1, ?> firstKeySelector,
			@Nullable final KeySelector<IN2, ?> secondKeySelector,
			final Context context) {
		checkNotNull(transformation);
		checkNotNull(firstInputTransformation);
		checkNotNull(secondInputTransformation);
		checkNotNull(operatorFactory);
		checkNotNull(context);

		final StreamGraph streamGraph = context.getStreamGraph();
		final String slotSharingGroup = context.getSlotSharingGroup();
		final int transformationId = transformation.getId();
		final ExecutionConfig executionConfig = streamGraph.getExecutionConfig();

		streamGraph.addCoOperator(
				transformationId,
				slotSharingGroup,
				transformation.getCoLocationGroupKey(),
				operatorFactory,
				firstInputTransformation.getOutputType(),
				secondInputTransformation.getOutputType(),
				transformation.getOutputType(),
				transformation.getName());

		if (firstKeySelector != null || secondKeySelector != null) {
			checkState(keyTypeInfo != null, "Keyed Transformation without provided key type information.");

			final TypeSerializer<?> keySerializer = keyTypeInfo.createSerializer(executionConfig);
			streamGraph.setTwoInputStateKey(
					transformationId,
					firstKeySelector,
					secondKeySelector,
					keySerializer);
		}

		final int parallelism = transformation.getParallelism() != ExecutionConfig.PARALLELISM_DEFAULT
				? transformation.getParallelism()
				: executionConfig.getParallelism();
		streamGraph.setParallelism(transformationId, parallelism);
		streamGraph.setMaxParallelism(transformationId, transformation.getMaxParallelism());

		for (Integer inputId: context.getStreamNodeIds(firstInputTransformation)) {
			streamGraph.addEdge(inputId, transformationId, 1);
		}

		for (Integer inputId: context.getStreamNodeIds(secondInputTransformation)) {
			streamGraph.addEdge(inputId, transformationId, 2);
		}

		return Collections.singleton(transformationId);

	}
}
